1. Field of the Invention
The present invention relates to wellbore completion. More particularly, the invention relates to an apparatus and method for expanding an expandable tubular assembly in a borehole.
2. Description of the Related Art
Expandable technology enables a smaller-diameter tubular to pass through a larger-diameter tubular, and thereafter be expanded to a larger diameter. In this respect, expandable technology permits the formation of a tubular string having a substantially constant inner diameter. When an expandable tubular is run into a borehole, it must be anchored within the borehole at the desired depth to prevent movement of the expandable tubular during the expansion process. Anchoring the expandable tubular within the borehole allows expansion of the length of the expandable tubular in the borehole.
The expandable tubular that is used to isolate the area of interest is often run into the borehole after previous strings of casing (e.g., parent casing) are already set within the borehole. The expandable tubular for isolating the area of interest must be run through the inner diameter of the parent casing to reach the portion of the open-hole borehole slated for isolation, which is located below the previously set parent casing. Accordingly, the outer diameter of the anchor and the expandable tubular must be smaller than the parent casing in the borehole in order to run through the parent casing to the depth at which the open-hole borehole exists. After locating the expandable tubular below the parent casing, a conventional expander tool is pushed or pulled through the expandable tubular to expand the anchor and the expandable tubular into contact with the surrounding borehole.
Oftentimes, it is desired to have the inner diameter of the expandable tubular to be at least as large as the inner diameter of the parent casing so that drilling can continue with the same drill bit. To achieve an inner diameter of the expandable tubular to be at least as large as the inner diameter of the parent casing, the expandable tubular may require a 28% expansion ratio. However, the conventional expander tool can typically obtain a 20% expansion ratio. Therefore, there is a need for an expansion system for expanding the expandable tubular to the required expansion ratio.